Field of the Invention
The present invention relates to a distance detecting device, an imaging apparatus, a distance detecting method and a parallax-amount detecting device.
Description of the Related Art
A distance detection technology applicable to digital cameras has been known which detects a distance by using a phase difference detection method using a ranging function in partial pixels of an image pickup device. The pixels include photoelectric conversion units which receive a luminous flux having passed through different regions of a pupil of an imaging optical system, and displaced amounts of image signals generated by the photoelectric conversion units are estimated, and a defocus amount is calculated for ranging.
When the plurality of photoelectric conversion units have different pupil transmittance distributions from each other, the image signals have different shapes from each other. As a result, the accuracy of estimation of displaced amounts of the image signals may decrease, which may lower the accuracy of ranging. Japanese Patent No. 3240648 discloses an image shape correction technique. A point spread function or line spread function for generating an image signal is used to generate an image correction filter. Performing convolution on an image signal with the image correction filter to correct a shape of the image so that the accuracy of ranging may be improved.
An image correction filter using a point spread function disclosed in Japanese Patent No. 3240648 is an isotropic two-dimensional filter and has a higher number of taps than those of a one-dimensional filter. As a result, the calculation scale of the image correction processing is increased, and the processing time is increased. An image correction filter using a line spread function is a one-dimensional filter so that the processing time is shortened but a component having a partial space frequency of an image signal may be corrected while a component having other different space frequency has a correction error. Thus, some image signals (target of imaging) may have variations in image correction effect, and the accuracy of ranging may decrease.